One card I would recommend, for combo lifegain, creature, and aura is a
Hopeful Eidolon or two. A nice 1/1 body with
lifelink that can be thrown out turn one, if necessary, or turn four as an aura.
Gift of Orzhova is another one I like, because it's a CMC 3 for +1/+1, flying, and
lifelink.